Wideband 1-bit reconfigurable transmission metasurface unit cell design in Ka-band with polarization hold and conversion.

In this paper, a wideband transmission unit cell is proposed for programmable metasurfaces operating in the Ka-band. The unit cell features a compact period of only 2.91 mm, corresponding to 0.34 λ0 at the center frequency of 35 GHz. A receiving layer, consisting of a patch loaded with two PIN diodes, is utilized to achieve 1-bit phase modulation, while a U-shaped patch serves as the transmitting layer to enable selection of linear polarization hold or conversion. Based on the multi-resonance principle, the proposed unit cell exhibits broadband behavior, as demonstrated by simulation results under periodic boundary conditions, which indicate a 3 dB transmission bandwidth of 29.4-40 GHz (30.5%). Two unit cells were fabricated and tested in a standard waveguide, with the minimum insertion loss of the two states tested being 1.2 dB and 3 dB bandwidths of 30.1-31.2 GHz and 33.5-38.5 GHz, respectively. The maximum 180° phase error is 10°, indicating the high quality of the proposed unit cell.

All-dielectric metalens for quasi-optical mode and polarization conversion.

Quasi-optical mode conversion technology plays a very important role in the development of high-power terahertz radiation sources. The ability of metamaterials to manipulate wave-front paves a new way in the field of quasi-optical mode conversion. In this paper, the approach for quasi-optical mode conversion by all-dielectric metalens and polarization conversion is proposed and investigated. Three metalens are designed to converter cylindrical waveguide TE01 mode to linear polarized (LP), left-hand circularly polarized (LHCP), and right-hand circularly polarized (RHCP) Gaussian beams at 350 GHz. Electromagnetic simulations show that the Gaussian mode contents of output waves from three metalens are all over 98% with high polarization contents. Furthermore, a metalens is designed for dual circularly polarized (DCP) which could convert cylindrical waveguide TE01 mode to LHCP and RHCP simultaneously. This work unveils the potential application for metalens in terahertz region.

Extreme strength observed in limpet teeth.

The teeth of limpets exploit distinctive composite nanostructures consisting of high volume fractions of reinforcing goethite nanofibres within a softer protein phase to provide mechanical integrity when rasping over rock surfaces during feeding. The tensile strength of discrete volumes of limpet tooth material measured using in situ atomic force microscopy was found to range from 3.0 to 6.5 GPa and was independent of sample size. These observations highlight an absolute material tensile strength that is the highest recorded for a biological material, outperforming the high strength of spider silk currently considered to be the strongest natural material, and approaching values comparable to those of the strongest man-made fibres. This considerable tensile strength of limpet teeth is attributed to a high mineral volume fraction of reinforcing goethite nanofibres with diameters below a defect-controlled critical size, suggesting that natural design in limpet teeth is optimized towards theoretical strength limits.

[Status of endothelial progenitor cell in murine model of Kawasaki disease].

OBJECTIVE: To assess whether the occurrence of coronary artery lesion was correlated with the changes of endothelial progenitor cell (EPC) number and function in murine model of Kawasaki disease (KD). METHODS: Lactobacillus casei cell wall extract (LCWE) was prepared and then C57BL/6 mice received a single intraperitoneal injection of LCWE for inducing KD. Twenty-four mice were categorized randomly into 3 groups: KD model group at Day 14 post-injection, KD model group at Day 56 post-injection and control group with an intraperitoneal injection of phosphate buffered solution (n = 8 each). The number of circulating EPC was defined as CD34(+)Flk-1(+)CD45(-) from mice. Meanwhile, bone marrow mononuclear cells were cultured in vitro to expand EPC for functional analysis. After 7 days of culturing, EPC were inoculated onto culture plate and thiazolyl blue assay was used to measure the absorbance value by enzyme labeling instrument to evaluate the proliferation. The adhesion of EPC was performed by replating cells on fibronectin coated dishes and then counting the number of adherent cells. The migration of EPC was assayed by Transwell. RESULTS: Focal inflammatory infiltrate was evident in coronary artery trunk and a series of branches at Day 14 post-injection. The inflammatory cell infiltrate consisted of mononuclear lymphocytes. The number of circulating EPC were significantly lower in the Day 14 LCWE-treating murine model versus the controls (0.017% ± 0.008% vs 0.028% ± 0.007%, P < 0.01). Disruption of elastin was consistently observed at Day 56 post-injection. And there was no apparent recovery in number of EPC (0.016% ± 0.007%, P < 0.01). When bone marrow mononuclear cells were cultured in vitro, the colony-forming ability of EPC decreased in the KD model group at Day 14 post-injection versus the controls. Test of proliferating ability showed that the absorbance was 0.39 ± 0.11 in MTT experiment and decreased than the controls (0.61 ± 0.14, P < 0.01). Adhesion and migration were also down-regulated versus the controls ((3.1 ± 0.6) and (3.2 ± 0.6) vs (6.4 ± 1.2) and (6.2 ± 0.5) cells/HPF, both P < 0.01). In the KD model group at Day 56 post-injection, the colony-forming ability of EPC was not recovered significantly. Proliferation ability, adhesion and migration were still decreased compared to the controls (0.38 ± 0.09, (3.12 ± 0.56) cells/HPF and (3.29 ± 0.63) cells/HPF, all P < 0.01). CONCLUSION: The occurrence of coronary artery lesion may be correlated with the down-regulation of EPC number and function in murine model of KD.

Endothelial progenitor cell transplantation ameliorates elastin breakdown in a Kawasaki disease mouse model.

BACKGROUND: Coronary artery damage from Kawasaki disease (KD) is closely linked to the dysfunction of endothelial progenitor cells (EPCs). The aim of the present study was to evaluate the therapeutic effect of EPCs transplantation in KD model. METHODS: Lactobacillus casei cell wall extract (LCWE)-induced KD model in C57BL/6 mice was established. The model mice were injected intravenously with bone marrow-derived in vitro expanded EPCs. Histological evaluation, number of circulating EPCs and the function of bone marrow EPCs were examined at day 56. RESULTS: Inflammation was found around the coronary artery of the model mice after 14 days, Elastin breakdown was observed after 56 days. CM-Dil labeled EPCs incorporated into vessel repairing foci was found. At day 56, the number of peripheral EPCs in the KD model group was lower than in EPCs transplanted and control group. The functional index of bone marrow EPCs from the KD model group decreased in proliferation, adhesion and migration. Increased number of circulating EPCs and improved function were observed on the EPCs transplanted group compared with model group. CONCLUSION: Exogenously administered EPCs, which represent a novel strategy could prevent the dysfunction of EPCs, accelerate the repair of coronary artery endothelium lesion and decrease the occurrence of aneurysm.

Endothelial progenitor cell down-regulation in a mouse model of Kawasaki disease.

BACKGROUND: Cardiovascular complications of Kawasaki disease (KD) are a common cause of heart disease in pediatric populations. Previous studies have suggested a role for endothelial progenitor cells (EPCs) in coronary artery lesions associated with KD. However, long-term observations of EPCs during the natural progression of this disorder are lacking. Using an experimental model of KD, we aimed to determine whether the coronary artery lesions are associated with down-regulation of EPCs. METHODS: To induce KD, C57BL/6 mice were administered an intraperitoneal injection of Lactobacillus casei cell wall extract (LCWE; phosphate buffered saline used as control vehicle). Study groups included: group A (14 days following LCWE injection), group B (56 days following LCWE injection) and group C (controls). Numbers of circulating EPCs (positively staining for both CD34 and Flk-1 while staining negative for CD45) were evaluated using flow cytometry. Bone marrow mononuclear cells were cultured in vitro to expand EPCs for functional analysis. In vitro EPC proliferation, adhesion and migration were assessed. RESULTS: The model was shown to exhibit similar coronary artery lesions to KD patients with coronary aneurysms. Numbers of circulating EPCs decreased significantly in the KD models (groups A and B) compared to controls ((0.017 ± 0.008)% vs. (0.028 ± 0.007)%, P < 0.05 and (0.016 ± 0.007)% vs. (0.028 ± 0.007)%, P < 0.05). Proliferative, adhesive and migratory properties of EPCs were markedly impaired in groups A and B. CONCLUSION: Coronary artery lesions in KD occur as a consequence of impaired vascular injury repair, resulting from excess consumption of EPCs together with a functional impairment of bone marrow EPCs and their precursors.

Optimized nanoscale composite behaviour in limpet teeth.

Limpet teeth are striking examples of a biological fibrous nanocomposite consisting of goethite mineral within a polymeric chitin matrix. The mechanical function of limpet teeth is critically dependent on the efficient composite behaviour of goethite, formed as distinct discontinuous nanofibres, reinforcing the matrix. The mechanical properties of discrete volumes from a limpet tooth measured using atomic force microscopy indicate how the tooth structure can be approximated as a short fibre-reinforced composite. Short fibre composite analysis reveals how the goethite nanofibres have a length optimized for the transfer of stress from the matrix to fibre and highlight how this limpet tooth structure is efficient in a mechanical load-bearing function.

In situ tensile testing of nanofibers by combining atomic force microscopy and scanning electron microscopy.

A nanomechanical testing set-up is developed by integrating an atomic force microscope (AFM) for force measurements with a scanning electron microscope (SEM) to provide imaging capabilities. Electrospun nanofibers of polyvinyl alcohol (PVA), nylon-6 and biological mineralized collagen fibrils (MCFs) from antler bone were manipulated and tensile-tested using the AFM-SEM set-up. The complete stress-strain behavior to failure of individual nanofibers was recorded and a diversity of mechanical properties observed, highlighting how this technique is able to elucidate mechanical behavior due to structural composition at nanometer length scales.